120 lines
2.9 KiB
C
120 lines
2.9 KiB
C
/* getcwd - get current working directory Author: Terrence W. Holm */
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/* Directly derived from Adri Koppes' pwd(1).
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* Modified by Andy Tanenbaum for POSIX (29 Oct. 1989)
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*/
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#include <lib.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <sys/dir.h>
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#include <string.h>
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#define getcwd _getcwd
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#define DIRECT_SIZE (sizeof (struct direct))
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PRIVATE _PROTOTYPE(void go_back, (char *path) );
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char *getcwd(buffer, size)
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char *buffer;
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int size;
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/* Get current working directory. */
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{
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int same_device, found, fd;
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char *r, path[PATH_MAX + 1], temp_name[NAME_MAX + 1];
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struct stat current, parent, dir_entry;
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struct direct d;
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if (buffer == (char *)NULL || size <= 0) {
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errno = EINVAL;
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return((char *)NULL);
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}
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path[0] = '\0';
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/* Get the inode for the current directory */
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if (stat(".", ¤t) == -1) return((char *)NULL);
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if ((current.st_mode & S_IFMT) != S_IFDIR) return((char *)NULL);
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/* Run backwards up the directory tree, grabbing dir names on the way. */
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while (1) {
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same_device = 0;
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found = 0;
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/* Get the inode for the parent directory */
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if (chdir("..") == -1) return((char *)NULL);
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if (stat(".", &parent) == -1) return((char *)NULL);
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if ((parent.st_mode & S_IFMT) != S_IFDIR) return((char *)NULL);
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if (current.st_dev == parent.st_dev) same_device = 1;
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/* At the root, "." is the same as ".." */
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if (same_device && current.st_ino == parent.st_ino) break;
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/* Search the parent directory for the current entry */
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if ((fd = open(".", O_RDONLY)) == -1) return((char *)NULL);
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while (!found && read(fd, (char *)&d, DIRECT_SIZE) == DIRECT_SIZE) {
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if (d.d_ino == 0L) continue; /* empty slot */
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if (same_device) {
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if (current.st_ino == d.d_ino) found = 1;
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} else {
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temp_name[0] = '\0';
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strncat(temp_name, d.d_name, NAME_MAX);
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if (stat(temp_name, &dir_entry) == -1) {
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close(fd);
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go_back(path);
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return((char *)NULL);
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}
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if (current.st_dev == dir_entry.st_dev &&
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current.st_ino == dir_entry.st_ino)
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found = 1;
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}
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}
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close(fd);
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if (!found) {
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go_back(path);
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return((char *)NULL);
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}
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if (strlen(path) + NAME_MAX + 1 > PATH_MAX) {
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errno = ERANGE;
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go_back(path);
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return((char *)NULL);
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}
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strcat(path, "/");
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strncat(path, d.d_name, NAME_MAX);
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current.st_dev = parent.st_dev;
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current.st_ino = parent.st_ino;
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}
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/* Copy the reversed path name into <buffer> */
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if (strlen(path) + 1 > size) {
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errno = ERANGE;
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go_back(path);
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return((char *)NULL);
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}
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if (strlen(path) == 0) {
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strcpy(buffer, "/");
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return(buffer);
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}
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*buffer = '\0';
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while ((r = strrchr(path, '/')) != (char *)NULL) {
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strcat(buffer, r);
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*r = '\0';
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}
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return(chdir(buffer) ? (char *)NULL : buffer);
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}
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PRIVATE void go_back(path)
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char *path;
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{
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/* If getcwd() gets in trouble and can't complete normally, reverse the
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* path built so far and change there so we end up in the directory that
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* we started in.
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*/
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char *r;
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while ((r = strrchr(path, '/')) != (char *)NULL) {
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chdir(r+1);
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*r = '\0';
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}
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}
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